|Publication number||US7186019 B2|
|Application number||US 10/526,052|
|Publication date||6 Mar 2007|
|Filing date||22 Aug 2003|
|Priority date||29 Aug 2002|
|Also published as||CN1678512A, CN100526206C, DE60325864D1, EP1532069A1, EP1532069B1, US20060039442, WO2004020328A1|
|Publication number||10526052, 526052, PCT/2003/3749, PCT/IB/2003/003749, PCT/IB/2003/03749, PCT/IB/3/003749, PCT/IB/3/03749, PCT/IB2003/003749, PCT/IB2003/03749, PCT/IB2003003749, PCT/IB200303749, PCT/IB3/003749, PCT/IB3/03749, PCT/IB3003749, PCT/IB303749, US 7186019 B2, US 7186019B2, US-B2-7186019, US7186019 B2, US7186019B2|
|Inventors||Gerd K. Binnig, Michel Despont, Mark A. Lantz, Peter Vettiger|
|Original Assignee||International Business Machines Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (5), Non-Patent Citations (2), Referenced by (13), Classifications (16), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application filed under 35 USC 371, is cross-referenced with, and claims priority from, International Patent Application PCT/IB2003/03749 filed on Aug. 22, 2003, and published in English with Publication No. WO 2004/020328 on Mar. 11, 2004, under PCT article 21(2), which in turn claims priority of EP 02019322.3, filed on Aug. 29, 2002.
The present invention generally relates to transducers for detecting movement of an article and particularly relates to transducers for detecting movement of an article in a Micro-Electro-Mechanical-System (MEMS) device.
An example of typical MEMS device is a local probe storage device as described in Vettiger et al. “The Millipede”—More than one thousand tips for future AFM data storage, P. Vettiger et al, IBM Journal of Research and Development. Vol. 44 No.3, May 2000. Such a device typically comprises a storage surface having a locally deformable film disposed thereon and an array of micro mechanical probe sensors each having a probe tip of atomic dimensions facing the coating. In operation, during a data write operation, the tips are brought into proximity to the storage surface. Energy is selectively applied to each tip, typically in the form of heating. The energy applied to the tips is transferred to the storage surface. The energy transfer produces a local deformation in the storage surface in the vicinity of each energized tip. The array of tips is moved in a scanning motion relative to the storage surface between successive write operations in preparation for writing to new locations on the storage surface. During a read operation, the arrays tips are urged against the storage surface. Simultaneously, the tips are again moved in a scanning motion relative to the storage surface. Local deformations of the storage surface produced during the aforementioned write operation produce deflections in the tips as they are scanned over the surface. Such deflections can be detected thermally or optically. The presence or absence of a local deformation in the storage surface by a tip can be detected as a stored “1” or stored “0”. The storage surface is mounted on an X-Y scanner to facilitate the scanning motions associated with the aforementioned reading and writing operations.
In operation, position error signals (PES) encoded in the storage surface facilitate sensing of the position and velocity of the storage surface relative to the tips. However, the PES data may be unavailable in some circumstances, such as upon initial start up of the device or during recovery of the device from a mechanical shock. To acquire the PES data, the scanner is first moved to a specified location and then scanning at a specified velocity is begun. However, to simplify such acquisition, it would be desirable to provide a transducer for movement sensing independently of the PES data in circumstances when the encoded PES signal is not available.
In accordance with the present invention, there is now provided a transducer for detecting movement of an article mounted for movement in a plane, the transducer comprising: a heater facing the plane of movement of the article and having a temperature dependent resistance; and, an edge defined in the article between regions of different thermal conductivity; wherein, as the article describes the movement, the edge moves relative to the heater producing a corresponding variation in heat loss from the heater and a corresponding variation in resistance of the heater.
The article may be mounted for translational movement in the plane. Alternatively, the article may be mounted for rotational movement in the plane. However, initially focussing on the translational case, the edge is preferably located in a plane surface of the article. In particularly preferred embodiments of the present invention, the edge is rectilinear. In a particularly preferred embodiment of the present invention, the heater preferably comprises an elongate body overlapping and extending parallel to the plane surface and perpendicular to the edge. This advantageously provides a surprisingly linear response to displacement of the article. Furthermore, in MEMS embodiments of the present invention to be described shortly, the response is surprisingly fast, thus allowing the use of relatively high bandwidth feedback for a range of servo control applications. The elongate body preferably comprises a silicon cantilever having a doped resistive region formed therein. The transducer technology of the present invention is thus conveniently compatible with other MEMS fabrication technologies. The edge may be located on the periphery of the plane surface. Alternatively, the edge is formed as a step in the plane surface.
The present invention also extends to a movement detection system for detecting movement of an article mounted for movement in a plane, the system comprising: first and second transducers as herein before described operative in opposite directions along a common axis of movement of the article in the plane. Preferably, the first and second transducers respectively face first and second parallel edges of the surface.
The present invention also extends to a movement detection system for detecting movement of an article mounted for movement in a plane, the system comprising: first and second transducers as herein before described operative in orthogonal directions of movement of the article in the plane. Preferably, in this instance, the first and second transducers respectively face first and second orthogonal edges of the surface. This arrangement advantageously facilitates measurement of displacements in two orthogonal directions independently without cross talk between the transducers.
In another embodiment of the present invention, the surface is mounted for rotational movement parallel to the heater about an axis of rotation. The edge may be in the form of a side of a slot formed in the surface and extending radially from the axis of the rotation. Alternatively, the surface may comprise a spoke extending radially from the axis of rotation and the edge comprises a side of the spoke.
Viewing the present invention from another aspect, there is now provided a method for detecting movement of an article mounted for movement in a plane, the method comprising: locating a heater having a temperature dependent resistance to face the plane of movement of the article; defining an edge in the article between regions of different thermal conductivity; and, detecting variation in resistance of the heater corresponding to variation in heat loss from the heater as the edge moves relative to heater during movement of the article in the plane.
Viewing the present invention from yet another aspect, there is now provided a local probe storage device comprising: storage surface, local probe storage array having a plurality of tips facing the storage surface; a scanner for moving the storage surface relative to the array in a plane parallel to the array; and a movement detection system as herein before described for detecting movement of the storage surface relative to the array.
This advantageously facilitates a stiffer scanner subassembly without sacrificing sensitivity. A sensitivity better than the pitch of data tracks on the storage surface, typically around 80 nm, permits start up and seek operations to a specified data track in reduced access times.
Preferred embodiments of the present invention will now described, by way of example only, with reference to the accompanying drawings, in which:
Referring first to
Referring now to
The difference in thermal conductivity between the first region 7 and the second region 8 may be implemented in many ways. For example, the second region 8 may be formed from or otherwise coated with a material having different thermal properties from those of the material from which the first region 7 is formed. Alternatively or additionally, one of the first and second regions may be perforated with pores or apertures thereby locally modifying the thermal properties of bulk material. In particularly preferred embodiments of the present invention, the second region 8 is constituted by an air gap. Such an air gap may constituted by introducing a recess into the surface 6, with edge 5 being in the form of a step. Alternatively, in particularly preferred embodiments of the present invention to be described shortly, the air gap may be provided by free space at the periphery of the surface 6, with the edge 5 being a peripheral edge of the surface 6.
Differences in thermal conductivity become significant on the micro meter or nano meter scale of especially preferred embodiments of the present invention. Turning to
In operation, a current is passed through the heater 4. The current flow causes heat generation in the heater 4. The resistance of the heater 4 is dependent on the temperature of the heater 4. The temperature of the heater 4 is dependent on the distance between the heater 4 and the surface 6. Accordingly, the temperature of the heater 4 is dependent of the position of the heater 4 relative to the surface 6. More specifically, the temperature of the heater 4 is dependent on the level of overlap between the heater 4 and the surface 6. The relationship between the temperature of the heater 4 and the surface 6 stems from conduction of heat energy from the heater 4 to the surface 6 through the intervening gap.
The efficiency of such conduction is dependent on the distance between the heater 4 and the surface 6. When the surface 6 is displaced in a direction parallel to the longitudinal axis of the sensor 3, the average distance from the heater 4 to the surface 6 is increased or decreased by virtue of the edge 5 formed on the surface 6. An increase or decrease in this distance produces a corresponding change in cooling efficiency of the heater 4. The change in cooling efficiency produces a corresponding change in resistance of the heater 4. In especially preferred embodiments of the present invention, the edge 5 of the surface 6 adjacent the heater 4 is both smooth and perpendicular to the direction of motion to be sensed such that any motion in this perpendicular direction produces no change in cooling efficiency and therefore no signal. Similarly, in particularly preferred embodiments of the present invention, the plane of the heater 4 is parallel to the plane of the surface 6 to provide an output signal which varies as a linear function of displacement of the article 1. The sensitivity of the transducer 3 is dependent on the spacing between the heater 4 and the surface 6.
In especially preferred embodiments of the present invention, the transducer 3 is made resistant to torsional forces in the interests of minimizing twisting of the transducer 3 by friction between the or each tip 10 and the surface 6. Such twisting may otherwise adversely affect the linearity of the transducer 3. The twin limb design of the transducer 3 described with reference to
As indicated earlier, the velocity and acceleration of the surface 6 can be calculated by taking the first and second derivatives of the voltage signal from the transducer 3. Referring now
In some environments, changes in ambient temperature and the like may give rise to undesirable DC drift in measurements obtained from a transducer 3 of the form herein before described. Such changes unsuitable for some applications. However, referring now to
In the preferred embodiments of the present invention herein before described a transducer 3 is provided for measuring displacement of an article along a single axis of motion. However, the present invention is equally applicable to measuring linear movement of an article 1 along more than one axis of motion. For example, referring now to
In some of the preferred embodiments of the present invention herein before described, the edge 5 of the surface 6 is provided by the periphery of the surface. However, referring to
As indicated earlier, with reference to
Referring now to
With reference to
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|U.S. Classification||374/6, G9B/9.003|
|International Classification||G11B9/00, G01N25/00, G01Q60/58, B81B3/00, G11B9/12|
|Cooperative Classification||B82Y35/00, G01Q60/58, B82Y10/00, G11B9/1418|
|European Classification||B82Y10/00, B82Y15/00, B82Y35/00, G11B9/14M, G01Q60/58|
|1 Aug 2005||AS||Assignment|
Owner name: INTERNATIONAL BUSINESS MACHINES CORPORATION, NEW Y
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:BINNING, GERD K.;DESPONT, MICHEL;LANTZ, MARK A.;AND OTHERS;REEL/FRAME:016603/0499;SIGNING DATES FROM 20050321 TO 20050516
|11 Oct 2010||REMI||Maintenance fee reminder mailed|
|6 Mar 2011||LAPS||Lapse for failure to pay maintenance fees|
|26 Apr 2011||FP||Expired due to failure to pay maintenance fee|
Effective date: 20110306